[FFmpeg-devel] [PATCH] libvorbis: use 0-10 range for audio quality

[Justin Ruggles]

Justin Ruggles wrote:
> Hi,
> 
> Nicolas George wrote:
>> Hi.
>>
>> The attached trivial patch changes the libvorbis encoder so that the range
>> for the -aq option is 0-10 instead of 0-1. My reasons for this change are:
>>
>> - The native vorbis encoder uses a similar factor:
>>   venc->quality = avccontext->global_quality / (float)FF_QP2LAMBDA / 10.;
> 
> I agree that the native and libvorbis encoders should be the same.
> 
>> - The command line oggenc uses the same 0-10 range.
> 
> This is a valid consideration. I chose 0.0 to 1.0 for libvorbis when I
> submitted the patch for the -aq option because lavc passes the quality
> setting directly to libvorbis, which uses 0.0 to 1.0.
> 
>> - The usual quality settings (3 for 112 kbps nominal, 4 for 128 kbps) are
>>   not exactly possible because 0.3?118 and 0.4?118 are not integers
>>   (118=FF_QP2LAMBDA); "Nominal bitrate: 127.728000 kb/s" lacks some
>>   elegance.
> 
> I don't see what this has to do with your patch.

Nevermind that last comment. I see it now. This is certainly a good
reason not to use small scales for -aq and I agree with the patch.

-Justin